The Lamarckian theory of inheritance of acquired characters has mostly remained unaccepted in mainstream biology due to the lack of irrefutable experimental evidence as well as insufficient explanatory support against the Weismann's doctrine of isolation of the germ line from soma (1–3). Interestingly, there has been of late a revival of interest in some sort of Lamarckism (4, 5). Recently, pattern of gene expression regulated by chromatin factors has been found to be inherited through germ line (6). Both repressing and activating modes of gene regulation are inherited mitotically throughout development as well as through meiosis. Further, alteration in chromatin state induced by a drug that reduces function of a heat-shock chaperone protein has most recently been found to be inheritable and to underlie morphological alterations in Drosophila (7). The present work is based on the concept that drug induced behavioral alteration in an established model organism like Drosophila may suitably be used as an adaptive response to test the validity of Lamarckism.
Chronic exposure to neuroactive drugs including those of human use and abuse produces long lasting changes in neuronal function and behavior (8–10). Neural plasticity underlies these changes (10–11). Most important, involvement of regulation of gene expression and chromatin structure has recently been demonstrated in synaptic plasticity (12). D. melanogaster has lately emerged as an attractive model to study drug induced behavior and addiction (13–14). Exposure to various neuroactive compounds is known to affect locomotor behavior in both Drosophila as well as mammalian models (14–16). Like mammals, dopaminergic pathways in Drosophila play a role in modulating locomotor behavior in response to neuroactive drugs (17). Of the present interest was to know if neuroactive drugs cause inheritable alteration in locomotor behavior in Drosophila. That the drugs cause altered locomotor activity is known (Sharma, 2003, a rapid procedure for screening of neuroactive substance using the fruitfly Drosophila melanogaster, patent applied; 14–16). Here, I examined if chronic exposure of flies to a range of neuroactive compounds including addictive, convulsant, and mood stabilizing drugs induce an inheritable change in locomotor behavior by systematically surveying two subsequent generations of drug exposed flies to see if they also exhibit abnormal locomotor behavior.